Patent application title: THERMAL PRINTER

Abstract:

A thermal printer in which a thermal head can be attached easily to a
print unit without requiring a tool such as a screw driver.
The thermal printer has a printing unit (40) having a left ribbon frame
(43) and a right ribbon frame (42) facing each other. A head housing (60)
is attached between the frames (42, 43) while supporting a thermal head
(12). A supporting-recess in the surface of the left ribbon frame (43)
faces the right ribbon frame (42) and supporting the left side face (64)
of the head housing (60). A frame cover (70) is fitted on and removed
from a fitting portion provided on the outer surface of the right ribbon
frame which is at the back side of the surface facing the left ribbon
frame (43) and the cover supporting a right side face (62) of the head
housing (60) through a through-hole (50a) formed on the right ribbon
frame (42).

Claims:

1. A thermal printer which prints by holding and conveying a printing
medium between a platen roller and a thermal head, the printer
comprising:a printing unit provided with a first and a second laterally
spaced away frame facing each other in a width direction of the printing
medium;a head housing supporting the thermal head and attached between
the first frame and the second frame;a supporting unit provided on a
surface on the first frame facing and opposing the second frame, the
supporting unit supporting a first side face of the head housing; anda
frame cover fitted on and removable from a fitting portion provided on an
outwardly facing surface of the second frame which is at an opposite side
from a surface facing the first frame and the frame cover supporting a
second side face of the head housing through a through-hole formed on the
second frame.

2. The thermal printer according to claim 1 further comprising a
support-recess for the head housing and formed on the second side face of
the head housing, and a supporting-protrusion on the frame cover and
fitted into the support-recess formed on the second side face of the head
housing through a through-hole on the second frame.

3. The thermal printer according to claim 2 wherein the supporting unit
supports the first side face of the head housing at a more upstream side
of the conveyance direction of the printing medium than the thermal head
and supporting the head housing at a rotational axis enabling the head
housing to rotate, and wherein,the support-recess formed on the second
side face of the head housing is in a round shape, with the rotational
axis supported by the supporting unit consistent with the axis of the
support-recess.

4. The thermal printer according to claim 1, wherein the thermal printer
performs printing by transferring ink from an ink ribbon onto the
printing medium, a ribbon supply shaft for supplying the ribbon and a
ribbon take-up shaft for taking-up the ribbon extend between the first
frame, and the second frame and are rotatably bridged over between the
first and second frame.

5. The thermal printer according to claim 4 further comprising a driving
force transferring mechanism for transferring a driving force to the
ribbon take-up shaft at the first frame; through-holes formed in the
frame cover respectively at the places corresponding to the ribbon
take-up shaft and the ribbon supply shaft.

6. The thermal printer according to claim 1, further comprising a
rotatable head pressure regulating unit configured for regulating the
head pressure of the thermal head by rotation of a regulating shaft
bridged over perpendicular to the first frame and the second frame, and
wherein a through-hole is formed in the frame cover at a place
corresponding to the regulating shaft.

Description:

CROSS REFERENCE TO RELATED APPLICATION

[0001]The present application is a 35 U.S.C. §§371 national
phase conversion of PCT/JP2008/068172 filed Oct. 6, 2008, which claims
priority of Japanese Application No. 2008-028684, filed Feb. 8, 2008, the
disclosure of which is incorporated by reference herein. The
International Application was published in the Japanese Language.

TECHNICAL FIELD

[0002]The present invention relates to a thermal printer which performs
printing by holding and conveying a printing medium between a platen
roller and a thermal head. More particularly, the present invention
relates to a thermal printer which performs printing using a thermal head
attached between a pair of frames facing each other in a width direction
of the printing medium.

BACKGROUND ART

[0003]In general, a thermal printer which performs printing using a
thermal head prints predetermined print data onto a printing medium by
holding and conveying a printing medium, such as a continuous label or a
continuous tag, between a platen roller and a thermal head. The thermal
head is supported by a printing unit such that a heat generating element
is opposing the platen roller.

[0004]In the past, the attachment of the thermal head to the printing unit
was performed by directly attaching the thermal head with a screw, or by
attaching it using a so called spacer, which is a joining member,
attached to the thermal head by a screw. (See, for example, Japanese
Unexamined Patent Application, First Publication H11-216889 for
reference).

[0005]However, in conventional technology, a tool, such as a screw driver,
was necessary when attaching the thermal head to the printing unit, and
there was a problem that the attaching process of the thermal head
becoming complicated.

SUMMARY OF INVENTION

Technical Problem

[0006]The present invention has been made in view of the aforementioned
problem. The object of the present invention is to provide a thermal
printer which can easily attach the thermal head to the printing unit
without requiring a tool such as a screw driver.

Solution to Problem

[0007]In order to solve the aforementioned problem, the thermal printer of
the present invention proposes the following arrangements.

[0008]An aspect of the present invention includes a thermal printer which
performs printing by holding and conveying a printing medium between a
platen roller and a thermal head. The printer comprises: a printing unit
provided with a first frame and a second frame facing each other in a
width direction of the printing medium. A head housing supports the
thermal head and is attached between the first frame and the second
frame. A supporting unit is provided on an opposing surface on the first
frame facing the second frame supporting a first side face of the head
housing. A frame cover is fitted on and removed from a fitting portion
provided on the outer surface of the second frame, which is at the back
side of the surface facing the first frame and supporting a second side
face of the head housing through a through-hole formed on the second
frame.

[0009]Another aspect of the present invention relates to the above thermal
printer support-recess for the head housing to be supported is formed on
the second side face of the head housing, and wherein a
supporting-protrusion fitted into the supported-recess formed on the
second side face of the head housing through the through-hole formed on
the second frame is formed on the frame cover.

[0010]Another aspect of the present invention relates to the above thermal
printer wherein the supporting unit supports the first side face of the
head housing at a more upstream side of the conveyance direction of the
printing medium than the thermal head as a rotational axis enabling to
move rotationally, and wherein, the supported-recess formed on the second
side face of the head housing is in a round shape, with the rotational
axis supported by the supporting unit consistent with the axis of the
supported-recess.

[0011]In yet another aspect of the present invention, the thermal printer
performs printing by transferring ink from an ink ribbon onto the
printing medium, and between the first frame and the second frame, a
ribbon supply shaft supplying the ribbon and a ribbon take-up shaft
taking-up the ribbon are rotatably bridged over.

[0012]In another aspect of the present invention, a driving force
transferring mechanism on the first frame transfers the driving force to
the ribbon take-up shaft, and through-holes are formed on the frame cover
respectively at the places corresponding to the ribbon take-up shaft and
the ribbon supply shaft.

[0013]In yet another aspect of the present invention, the thermal printer
is provided with a head pressure regulating unit regulating the head
pressure of the thermal head by the rotational movement of a regulating
shaft bridged over in a direction perpendicular to the first frame and
the second frame, and a through-hole is formed on the frame cover at a
place corresponding to the regulating shaft.

ADVANTAGEOUS EFFECTS OF INVENTION

[0014]The thermal printer of the present invention comprises: a printing
unit provided with a first frame and a second frame facing each other in
a width direction of the printing medium; a head housing supporting the
thermal head and attached between the first frame and the second frame; a
supporting unit provided on an opposing surface on the first frame facing
the second frame supporting a first side face of the head housing; and a
frame cover fitted on and removed from a fitting portion provided on the
outer surface of the second frame which is at the back side of the
surface facing the first frame and supporting a second side face of the
head housing through a through-hole formed on the second frame.

[0015]In this way, the thermal printer of the present invention enables
easy attaching and detaching of the head housing supporting the thermal
head, by only fitting on and removing the frame cover from the outer
surface of the second frame. In addition, the thermal printer of the
present invention enables easily attaching the thermal head to the
printing unit without requiring a tool such as a screw driver.

[0016]Furthermore, the thermal printer of the present invention is
configured such that a supported-recess for the head housing to be
supported is formed on the second side face of the head housing, and a
supporting-protrusion on the frame cover is fitted into the
supported-recess formed on the second side face of the head housing
through the through-hole formed on the second frame. In this way, the
thermal printer of the present invention achieves an effect of accurately
positioning the head housing supporting the thermal head by removably
fitting the frame cover to the outer surface of the second frame.

[0017]Furthermore, the thermal printer of the present invention is
configured such that the supporting unit supports the first side face of
the head housing upstream in the conveyance direction of the printing
medium of the thermal head as a rotational axis enabling to move
rotationally. The supported-recess formed on the second side face of the
head housing is in a round shape, with the rotational axis supported by
the supporting unit consistent with the axis of the supported-recess. In
this way, the thermal printer of the present invention can rotatably
support the thermal head by only removably fitting the frame cover to the
outer surface of the second frame, thereby simplifying the mechanism
pressing the thermal head to the platen roller.

[0018]Furthermore, the thermal printer of the present invention is
configured such that a ribbon take-up shaft and a ribbon supply shaft are
rotatably bridged over between the first frame and the second frame. In
this way, the thermal printer of the present invention can use the ribbon
frames, where the ribbon take-up shaft and the ribbon supply shaft are
bridged over, also as a structure supporting the thermal head, thereby
achieving the effects of cost reduction by reducing the number of parts,
and downsizing the thermal printer.

[0019]Still further, the thermal printer of the present invention is
configured such that on the first frame, a driving force transferring
mechanism transferring the driving force to the ribbon take-up shaft is
provided, and the through-holes are formed respectively at the places on
the frame cover corresponding to the ribbon take-up shaft and the ribbon
supply shaft. Even in a state with the frame cover fitted to the outer
surface of the second frame, it is possible to achieve the effect of
easily regulating the ribbon take-up shaft and the ribbon supply shaft
through the through-holes formed on the frame cover from the second frame
side where the driving force transferring mechanism is not provided.

[0020]Furthermore, the thermal printer of the present invention is
configured with a head pressure regulating unit regulating the head
pressure of the thermal head by the rotational movement of a regulating
shaft bridged over in a direction perpendicular to the first frame and
the second frame, and a through-hole is formed on the frame cover at a
place corresponding to the regulating shaft. In this way, even in a state
with the frame cover fitted to the outer surface of the second frame, it
is possible to achieve the effect of easily regulating the head pressure
from the second frame side by operating the regulating shaft through the
through-hole formed on the frame cover.

BRIEF DESCRIPTION OF DRAWINGS

[0021]FIG. 1 is a schematic side view diagram showing the configuration of
the thermal printer in the embodiment of the present invention.

[0022]FIG. 2 is an external perspective view diagram showing the closed
state of the thermal printer in the embodiment of the present invention.

[0023]FIG. 3 is an external perspective view diagram showing the opened
state of the thermal printer in the embodiment of the present invention.

[0024]FIG. 4(a) is a front perspective view diagram showing the
configuration of the head housing shown in FIG. 3 from the front side.

[0025]FIG. 4(b) is a front perspective view diagram showing the
configuration of the head housing shown in FIG. 3 from the front side.

[0026]FIG. 4(c) is a rear perspective view diagram showing the
configuration of the head housing shown in FIG. 3 from the rear side.

[0027]FIG. 5 is a perspective view diagram showing the configuration of
the printing unit shown in FIG. 3.

[0028]FIG. 6 is a perspective view diagram showing the configuration of
the frame cover shown in FIG. 3.

[0029]FIG. 7 is a perspective view diagram showing the attachment
operation of the head housing to the printing unit shown in FIG. 3.

[0030]FIG. 8 is a perspective view diagram showing the head housing in an
attached state to the printing unit shown in FIG. 3.

[0031]FIG. 9 is an illustration to explain the supported state of the head
housing attached to the printing unit shown in FIG. 3.

DESCRIPTION OF EMBODIMENTS

[0032]Hereinafter, an embodiment of the present invention is described in
detail based on the drawings.

[0033]With reference to FIG. 1, the thermal printer 10 of the present
embodiment is provided with a platen roller 11, and a thermal head 12
arranged such that the surface (hereinafter called as printing surface)
on which a plurality of heat generating element is formed in the widths
direction is facing the platen roller 11, together defining a printing
unit. The thermal printer 10 is configured to layer a printing medium 1
such as a continuous label strip with a plurality of labels temporarily
attached on a strip form backing sheet, and an ink ribbon 2, then hold
and convey them between the platen roller 11 and the thermal head 12.
Then the thermal printer 10 performs printing by transferring the ink to
the printing medium 1 from an ink ribbon 2 by selectively generating heat
of the heat generating element in the thermal head 12.

[0034]The printing medium 1, is in a state wound in a roll to define a
tubular body such as a paper tube, that is, a roll of paper 3, is
rotatably supported at the supply unit 13. The printing medium 1 is
supplied between the platen roller 11 and the thermal head 12 from the
supply unit 13. In addition, the ink ribbon 2 is laid between a ribbon
take-up shaft 14 which is rotationally driven interlocking with the
platen roller 11, and a ribbon supply shaft 15. The ink ribbon 2, in a
state wound in a roll supported at the ribbon supply shaft 15, is
supplied between the platen roller 11 and the thermal head 12 together
with the printing medium 1. After transferring the ink, the ink ribbon 2
is taken-up by the ribbon take-up shaft 14.

[0035]Furthermore, the thermal printer 10 is provided with a main unit 20,
of which an upper portion is opened, and having a platen roller 11 and a
supply unit 15, an upper cover unit 30 covering the upper portion of the
main unit 20, and a printing unit 40, arranged between the main unit 20
and the upper cover unit 30, having a thermal head 12, a ribbon take-up
shaft 14, and a ribbon supply unit 15. The upper cover unit 30 and the
printing unit 40 are supported to rotate open and closed by the
supporting shaft 17 provided at the back side of the main unit 20. In
addition, the upper cover unit 30 and the printing unit 40 are configured
such that they may be opened from the front side where the outlet 16
discharges the printed print medium.

[0036]In FIG. 2, the thermal printer 10 in a closed state with the upper
cover unit 30 closed is shown. In this closed state, the printing unit 40
is positioned between the main unit 20 and the upper cover unit 30. As
shown in FIG. 1, in this closed state, the printing unit 40 is positioned
so that the thermal head 12, which is provided at the printing unit 40,
is pushed against the platen roller 11, which is provided at the main
body 20. Furthermore, the printing unit 40 is configured such that can be
fitted into the upper cover unit 30. In the closed state shown in FIG. 2,
the printing unit 40 is in a fitted state fitted into the upper cover
unit 30.

[0037]In FIG. 3, the thermal printer 10 is shown in an opened state with
the upper cover unit 30 opened. In this opened state, it is possible to
respectively rotate the upper cover unit 30 and the printing unit 40
independently. The upper cover unit 30 is configured such that it is
maintained at the opened state shown in FIG. 3 by the opening and closing
stopper 31, even if an operator's hands are released from it. In
addition, an arm portion 41 of the printing unit 40 engages the protruded
portion 31a which in turn protrudes inside the opening and closing
stopper 31, thereby enabling holding the upper cover unit 30
independently from the printing unit 40 in a state as shown in FIG. 3.
Furthermore, at the upper cover unit 30, a not shown abutting member
maintains the printing unit 40 in a fitted state by resiliently abutting
to the printing unit 40. When opening the upper cover unit 30 from the
closed state shown in FIG. 2, the printing unit 40, in a fitted state,
rotates together with the upper cover unit 30, to be in the opened state
shown in FIG. 3 by pulling the printing unit 40 out from the upper cover
unit 30.

[0038]The thermal head 12 is configured such that it is attached to the
printing unit 40 supported by the head housing 60. Referring to FIG. 4,
the head housing 60 is provided with a round shape support-recess 61a
arranged at a more upstream side of the conveyance direction of the
printing medium 1 than the thermal head 12 (the heat generating element
formed), and a right side face 62 (the second side face) where a round
shape support-recess 61b, having the diameter of the support-recess 61,
and being arranged at a downstream side of this support-recess 61a. In
addition, the head housing has a round shape support-protrusion 63a (a
supporting unit) arranged at a more upstream side of the conveyance
direction of the printing medium 1 than the thermal head 12, and a left
side face 64 (the first side face) with a round shape support-protrusion
63b with a diameter smaller than that of the support-protrusion 63a, and
arranged downstream of this support-protrusion 63a. The support-recess
61a of the right side face 62 and the supported-protrusion 63a of the
left side face 64 face each other such that the axes coincide. The
support-recess 61b of the right side face 62 and the support-protrusion
63b of the left side face 64 are formed face each other such that the
axes coincide.

[0039]Furthermore, a lower surface 65 of the head housing 60 functions as
a guide surface which leads the ink ribbon 2 between the platen roller 11
and the thermal head 12 from the ribbon supply shaft 15.

[0040]The thermal head 12 is fixed at the head housing 60. A pressing
member 66 at the back side of the printing surface of the thermal head 12
abuts the after-mentioned head pressure regulating unit when attaching
the head housing 60 to the printing unit 40. The pressing member is
supported movably in a direction perpendicular to the printing presses
the thermal head 12 fixed to the head housing 60 against the platen
roller 11. FIG. 4 (c) shows a connector 68 of the thermal head 12.

[0041]Referring to FIGS. 3 and 5, the printing unit 40 is on the open end
side of the arm portion 41, and the other end of portion 41 is supported
by the supporting shaft 17. The arm portion 41 has a right ribbon frame
42 (the second frame) and a left ribbon frame 43 (the first frame), where
the ribbon take-up shaft 14 and the ribbon supply shaft 15 are
respectively bridged over in a rotatable manner. The distance between the
right ribbon frame 42 and the left ribbon frame 43 is set slightly larger
than the width of the head housing 60, which enables attachment of the
head housing 60 between the right ribbon frame 42 and the left ribbon
frame 43. In addition, on the upper pressing member 66 side of the
attached head housing 60, a regulating shaft 44 is bridged over in a
direction perpendicular to the right ribbon frame 42 and the left ribbon
frame 43. A head pressure regulating unit is attached to this regulating
shaft 44 and comprises an eccentric member 45 abutting the pressing
member 66 of the head housing 60 for regulating the pressing force of the
thermal head 12 to the platen roller 11 by the eccentric member 45
regulating the position of the pressing member 66 of the head housing 60.

[0042]On the left ribbon frame 43, there is a driven gear 46, which is
engaged with a driving gear 21 in FIG. 3, which is rotationally driven
with the platen roller 11 in the closed state shown in FIG. 2. Also
located on the left ribbon frame 43, is a not shown driving force
transferring mechanism, such as a gear, which transfers the rotational
driving force from the driven gear 46 to the ribbon take-up shaft 14. On
the surface of the left ribbon frame 43 facing the right ribbon frame 42,
is a round shape supporting-recess 47a, where a support-protrusion 63a is
fitted and the recess has almost the same diameter as the
supported-protrusion 63a formed on the left side face 64 of the head
housing 60, is formed. Also, on the surface of the left ribbon frame 43
facing the right ribbon frame 42, is a round shape supporting-recess 47b,
where a support-protrusion 63b is loosely fitted and having a larger
diameter than the support-protrusion 63b formed on the left side face 64
of the head housing 60.

[0043]On the outer surface of the right ribbon frame 42 which is at the
back side of the surface facing the left ribbon frame 43, there is a
frame rim 48 perpendicular to the outer surface, and formed on the outer
edges. The region surrounded by the frame rim 48 functions as a fitting
portion 49 in which it is possible to fit and remove a frame cover 70
shown in FIG. 6. The frame cover 70 is a plate-like member made of resin.
The shapes of the fitting portion 49 and the frame cover 70 are
asymmetric, so that the frame cover 70 is fitted to the fitting portion
49 in a specific orientation.

[0044]Referring to FIG. 5, the ribbon take-up shaft 14, the ribbon supply
shaft 15, and the regulating shaft 44 project through the right ribbon
frame 42 at the fitting portion 49. Also, the frame cover 70 has
through-holes 71, 72, and 73, through which the ribbon take-up shaft 14,
the ribbon supply shaft 15, and the regulating shaft 44 project beyond
the fitting portion 49. When the frame cover 70 is fitted to the fitting
portion 49, it is possible to operate the ribbon take-up shaft 14, the
ribbon supply shaft 15, and the regulating shaft 44. Furthermore, the
ribbon take-up shaft 14, the ribbon supply shaft 15, and the regulating
shaft 44 may be operated by a tool such as a dedicated tool or a screw
driver, through the through-holes 71, 72 and 73 formed at places
corresponding to the ribbon take-up shaft 14, the ribbon supply shaft 15,
and the regulating shaft 44 without those shafts projecting 44. In
addition, if the driving force transferring mechanism is not in the way,
the ribbon take-up shaft 14, the ribbon supply shaft 15, and the
regulating shaft 44 may be configured to be operated from the left ribbon
frame 43 side.

[0045]Furthermore, in the right ribbon frame 42 at the fitting portion 49,
a through-hole 50a and a through-hole 50b are formed at the places
corresponding respectively to the support-recess 61a and the
support-recess 61b which are formed on the right side face 62 of the
attached head housing 60. Also, on the frame cover 70 in FIG. 6, a round
shape support-protrusion 74, having a diameter about the same as the
support-recess 61a formed on the right side face 62 of the head housing
60, is fitted into the support-recess 61a through a through-hole 50a when
fitting the frame cover 70 to the fitting portion 49, is formed.
Furthermore, on the frame cover 70, there is a round shape
support-protrusion 75, having a smaller diameter than that of the
support-recess 61b formed on the right side face 62 of the head housing
60, and the protrusion 75 is loosely fitted to the support-recess 61b
through a through-hole 50b when fitting the frame cover 70 to the fitted
portion 49.

[0046]Furthermore, on the side face of the frame cover 70 that faces the
frame rim 48 when fitted together, there are two widely spaced resin
spring portions 76 which are displaced in a direction perpendicular to
the frame rim 48. Engaging projections 77 are formed at the resin spring
portions 76. On the frame rim 48, respective notches 51 are formed at
places opposing the resin spring portions 76, such that it is possible to
operate the resin spring portions 76 of the frame cover 70 when fitting.
Engaging recesses 52, engaging with the engaging projections 77 when
fitting, are formed near the notch 51. In addition, in this embodiment,
the engaging recesses 52 are formed as the through-holes penetrating
through the frame rim 48.

[0047]Next, attaching the head housing 60 to the printing unit 40 is
described with reference to FIGS. 7 and 8.

[0048]FIG. 7 is a perspective view diagram showing the attachment
operation of the head housing 60 to the printing unit shown in FIG. 3.
FIG. 8 is a perspective view diagram showing the head housing 60 in an
attached state to the printing unit shown in FIG. 3. FIG. 9 is an
illustration to explain the supported state of the head housing attached
to the printing unit shown in FIG. 3.

[0049]In the attachment first, the support-protrusion 63a formed on the
left side face 64 of the head housing 60 is fitted to the support-recess
47a formed on the surface facing the left ribbon frame 43. At the same
time, the support-protrusion 63b formed on the left side face 64 of the
head housing 60 is loosely fitted to the support-recess 47b formed on the
opposing surface of the left ribbon frame 43. Then, as shown in FIG. 7,
the head housing 60 is inserted to a predetermined position between the
right ribbon frame 42 and the left ribbon frame 43. In this way, the left
side face 64 of the head housing 60 will be in a state almost set and
supported at a position against the opposing surface of the left ribbon
frame 43. In addition, the support-recess 61a and the support-recess 61b,
which are formed on the right side face 62 of the head housing 60, will
be in a state respectively facing the through-hole 50a and the
through-hole 50b, which are formed on the right ribbon frame 42.

[0050]Next, as shown in FIG. 8, by pressing the resin spring portions 76
formed on the side faces as shown by the arrows in FIG. 7, the frame
cover 70 is fitted to the fitting portion 49, then the resin spring
portions 76 are released. In this way, the engaging projections 77 formed
at the resin spring portions 76 are engaged with the engaging-recesses 52
formed on the frame rim 48, and the frame cover 70 is locked in a state
fitted to the fitting portion 49.

[0051]To fit the frame cover 70 to the fitting portion 49, the
support-protrusion 74 formed on the frame cover 70 is fitted to the
support-recess 61a through the through-hole 50a. At the same time, the
support-protrusion 75 formed on the frame cover 70 is loosely fitted to
the support-recess 61b through the through-hole 50b. In this way, as
shown in FIG. 9, the head housing 60 is supported with the support-recess
61a of the right side face 62 and the support-protrusion 63a of the left
side face 64 both having a consistent axis, in a state respectively
fitted to the support-protrusion 74 of the frame cover 70 and to the
support-recess 47a of the left ribbon frame 43. At the same time, the
support-recess 61b of the right side face 62 and the support-protrusion
63b of the left side face 64 both having a consistent axis, are
respectively loosely fitted and supported by the support-protrusion 75 of
the frame cover 70 and the support-recess 47b of the left ribbon frame
43. Accordingly, the head housing 60 is supported such that, as shown by
an arrow A, it is possible to rotate the support-recess 61a of the right
side face 62 and the support-protrusion 63a of the left side face 64
within the allowance range of the support-recess 61b of the right side
face 62 and the support-protrusion 63b of the left side face 64 in the
loosely fit state. Therefore, the thermal head 12 is pressed to the
platen roller 11 by the biasing force of the spring 67 provided between
the pressing member 66 abutting to the eccentric member 45 and the
thermal head 12 fixed to the head housing 60.

[0052]In addition, the ribbon take-up shaft 14, the ribbon supply shaft
15, and the regulating shaft 44 projecting out to the fitting portion 49,
are inserted respectively into the through-holes 71, 72 and 73 which are
formed on the frame cover 70. Therefore, it is possible to respectively
operate the ribbon take-up shaft 14, the ribbon supply shaft 15 and the
regulating shaft 44 through the through-holes 71, 72 and 73.

[0053]Detaching the head housing 60 attached to the printing unit 40 is
performed in a reverse procedure of the attachment of the head housing 60
to the printing unit 40. In other words, by pressing the resin spring
portions 76 formed on the side surface of the frame cover 70 through the
notches 51, the engagement of the engaging projections 77, formed on the
resin spring portions 76, with the engaging recesses 52, formed on the
frame rim 48, are released. Then, by pressing the resin spring portions
76 formed on the side surfaces, the frame cover 70 is detached from the
fitting portion 49. In this way, it is possible to detach the head
housing 60 from between the right ribbon frame 42 and the left ribbon
frame 43.

[0054]Furthermore, the present embodiment is configured to provide the
support-recess 47a and support-recess 47b on the opposing surface of the
left ribbon frame 43, and the support-protrusion 63a and the
support-protrusion 63b on the left side face 64 of the head housing 60.
However, the support-protrusions may be provided on the opposing surface
of the left ribbon frame 43, and the support-recesses may be provided on
the left side face 64 of the head housing 60. In addition, in the present
embodiment, the support-recess 47a formed on the opposing surface on the
left ribbon frame 43 is configured in a round shape of which the diameter
is larger than that of the support-protrusion 63b formed on the left side
face 64 of the head housing 60. Together with this, in the present
embodiment, the support-recess 61b formed on the right side face 62 of
the head housing 60 is configured such that it is in a round shape of
with a diameter larger than that of the support-recess 75 formed on the
frame cover 70. However, the shape of the support-recess 47a and the
support-recess 61b may be in an elongated shape hole to guide the
rotational movement of the head housing 60.

[0055]As explained above, according to the present embodiment, the thermal
printer 10 comprises a printing unit 40 provided with a left ribbon frame
43 and a right ribbon frame 42 facing each other; a head housing 60
supporting the thermal head 12 and attached between the left ribbon frame
43 and the right ribbon frame 42; a supporting-recess 47a provided on an
opposing surface on the left ribbon frame 43 facing the right ribbon
frame 42 supporting a left side face 64 of the head housing 60; and a
frame cover 70 fitted and removed to and from a fitting portion 49
provided on the outer surface of the right ribbon frame 42 which is at
the back side of the surface facing the left ribbon frame 43 and
supporting a right side face 62 of the head 60 housing through a
through-hole 50a formed on the right ribbon frame 42. The thermal printer
10 of the present embodiment enables easily attaching and detaching the
head housing 60 supporting the thermal head 12 by only fitting and
removing the frame cover 70 to and from the outer surface of the right
ribbon frame 42. In addition, the thermal printer 10 of the present
embodiment achieves an effect of easily attaching the thermal head 12 to
the printing unit 40 without requiring a tool such as a screw driver.

[0056]Furthermore, according to the present embodiment, the thermal
printer 10 is configured such that a support-recess 61a for the head
housing 60 to be supported is formed on the right side face 62 of the
head housing 60, and on the frame cover 70, a support-protrusion 74
fitted into the support-recess 61a formed on the right side face 62 of
the head housing 60 through the through-hole 50a formed on the right
ribbon frame 42 is formed. In this way, the thermal printer 10 of the
present embodiment achieves an effect of accurately performing
positioning of the head housing 60 supporting the thermal head 12 by
removably fitting the frame cover 70 to the outer surface of the right
ribbon frame 42.

[0057]Furthermore, according to the present embodiment, the thermal
printer 10 is configured such that the support-recess 47a provided on the
left side face 64 of the head housing 60 supports the left side face 64
of the head housing 60 at a more upstream side of the conveyance
direction of the printing medium 1 than the thermal head 12 as a
rotational axis enabling to move rotationally, and the support-recess 61a
formed on the right side face 62 of the head housing 60 is in a round
shape, with the rotational axis of the support-recess 47 is consistent
with the axis of the support-recess 61a. In this way, the thermal printer
10 of the present embodiment can rotatably support the thermal head 12 by
removably fitting the frame cover 70 only to the outer surface of the
right ribbon frame 42, thereby achieving an effect of simplifying the
mechanism pressing the thermal head 12 to the platen roller 11.

[0058]Furthermore, according to the present embodiment, a ribbon take-up
shaft 14 and a ribbon supply shaft 15 are rotatably bridged over between
the left ribbon frame 43 and the right ribbon frame 42. In this way, the
thermal printer 10 of the present embodiment can use the left ribbon
frame 43 and the right ribbon frame 42, where the ribbon take-up shaft 14
and the ribbon supply shaft 15 are bridged over, also as a support for
the thermal head 12, thereby achieving the effects of cost reduction by
reducing the number of parts, and downsizing of the thermal printer 10.

[0059]Still furthermore, according to the present embodiment, the thermal
printer 10 has a driving force transferring mechanism on the left ribbon
frame 43 for transferring the driving force to the ribbon take-up shaft
14, and on the frame cover 70, the through-holes 71 and 72 are formed
respectively at the places corresponding to the ribbon take-up shaft 14
and the ribbon supply shaft 15. In this way, the thermal printer 10, even
in a state with the frame cover 70 fitted to the outer surface of the
right ribbon frame 42, makes it possible to achieve the effect of easily
regulating the ribbon take-up shaft 14 and the ribbon supply shaft 15
through the through-holes 71 and 72 formed on the frame cover 70 from the
right ribbon frame 42 side where the driving force transferring mechanism
is not provided.

[0060]Furthermore, the thermal printer 10 of the present embodiment is
configured with a head pressure regulating unit regulating the head
pressure of the thermal head 12 by the rotational movement of a
regulating shaft 44 bridged over in perpendicular direction to the left
ribbon frame 43 and the right ribbon frame 42, and on the frame cover 70,
a through-hole 73 is formed at a place corresponding to the regulating
shaft 44. In this way, the thermal printer 10 of the present embodiment,
even in a state with the frame cover 70 fitted to the outer surface of
the right ribbon frame 42, makes it possible to achieve the effect of
easily regulating the head pressure from the right ribbon frame 42 side
by operating the regulating shaft 44 through the through-hole 73 formed
on the frame cover 70.

[0061]While the present invention has been described in relation to the
above embodiment thereof, it is not to be considered as limiting, and
that it is apparent that other variations and modifications may be made
within the scope of the technological thoughts of the present invention.
The numbers, positions, and forms, etc. of the above configuring
components are not to be limited to the above embodiment, and may be
modified to preferable numbers, positions, and forms, etc. The same
reference number is used for the same configuration components in each
diagram.